the terror plot is called, very active, led by osama bin laden's former personal secretary. u.s. embassies in the middle east shut their doors today and a travel alert is in effect for americans traveling abroad. devin dwyer has more. >> u.s. ben biases today looked like siege behinds across the middle east. in yemen, american troops ring the compound, patting down passersby. from western africa to bangladesh, a 7,000-mile security belt was pulled tight. leaving 22 u.s. embassies and consulates dark and empty. >> there's a significant threat stream, and we're reacting to it. >> u.s. intelligence has intercepted al qaeda communications about an attack on strategic significant american interests but the exact target remains unclear. >> we received information that high-level people from al qaeda in the arabian peninsula are talking about a major attack. >> one official told abc news the part that is alarming is the confidence they showed while communicating and the air of certainty. one major worry, explosives placed inside suicide bombers. we're concerned about century include imp